/* www.MicroDigitalEd.com
 * P6_8.c Testing nested interrupts

 * Timer1 is setup to interrupt at 1 Hz. In timer interrupt handler, 
 * the red LED is turned on and a delay function of 350 ms is called. 
 * The red LED is turned off at the end of the delay.
 *
 * Timer2 is setup to interrupt at 10 Hz. In timer interrupt handler, 
 * the blue LED is turned on and a delay function of 20 ms is called.
 * The blue LED is turned off at the end of the delay.
 *
 * When Timer1 has higher priority (the way this code is), the Timer2 
 * interrupts are blocked by Timer1 interrupt handler. You can see 
 * that when the red LED is on, the blue LED stops blinking.
 *
 * When Timer2 has higher priority (you need to switch the priority of
 * the two timers at the #defines), the Timer1 interrupt handler is 
 * preempted by Timer2 interrupts and the blue LED is blinking all the time.
 *
 * Tested with Keil 5.20 and MSP432 Device Family Pack V2.2.0
 * on XMS432P401R Rev C.
 */

#include "msp.h"

void Timer1_init(void);
void Timer2_init(void);
void delayMs(int n);

int main (void) {
    __disable_irq();
 
    /* initialize P2.2, P2.0 for blue and red LED */
    P2->SEL1 &= ~5;         /* configure P2.2, P2.0 as simple I/O */
    P2->SEL0 &= ~5;
    P2->DIR |= 5;           /* P2.2, P2.0 set as output */
    
    Timer1_init();
    Timer2_init();

    __enable_irq();

    while(1) { /*wait here for interrupt */
    }
}

void T32_INT1_IRQHandler(void) {
    P2->OUT |= 4;             /* turn on blue LED */
    delayMs(350);
    P2->OUT &= ~4;            /* turn off blue LED */
    TIMER32_1->INTCLR = 0;    /* clear raw interrupt flag */
}

void T32_INT2_IRQHandler(void) {
    P2->OUT |= 1;             /* turn on red LED */
    delayMs(20);
    P2->OUT &= ~1;            /* turn off red LED */
    TIMER32_2->INTCLR = 0;    /* clear raw interrupt flag */
}

/* priority of Timer1 and Timer2 should be between 0 and 7 */
#define PRIO_TMR1 2
#define PRIO_TMR2 3

void Timer1_init(void) {
    TIMER32_1->CONTROL = 0xC2;      /* no prescaler, periodic mode, 32-bit timer. */
    TIMER32_1->LOAD = 3000000-1;    /* set the reload value for 1 Hz */
    TIMER32_1->CONTROL |= 0x20;     /* enable interrupt */

    NVIC_SetPriority(T32_INT1_IRQn, PRIO_TMR1);
    NVIC_EnableIRQ(T32_INT1_IRQn);      /* enable interrupt in NVIC */
}

void Timer2_init(void) {
    TIMER32_2->CONTROL = 0xC2;      /* no prescaler, periodic mode, 32-bit timer. */
    TIMER32_2->LOAD = 300000-1;	    /* set the reload value for 10 Hz */
    TIMER32_2->CONTROL |= 0x20;     /* enable interrupt */

    NVIC_SetPriority(T32_INT2_IRQn, PRIO_TMR2);
    NVIC_EnableIRQ(T32_INT2_IRQn);  /* enable interrupt in NVIC */
}

/* delay n milliseconds (3 MHz CPU clock) */
void delayMs(int n) {
    int i, j;
    for(i = 0 ; i < n; i++)
        for(j = 0; j < 750; j++)
            {}  /* do nothing for 1 ms */
}